<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        //目标
        class Dep{
            constructor(){
                this.subs = [];
            }
            //添加观察者
            addSub(sub){
                if(sub&&sub.update){
                    this.subs.push(sub)
                }
            }
            //发布通知
            notify(){
                this.subs.forEach(sub=>{
                    sub.update()
                })
            }
        }
        //观察者
        class Watcher{
            update(){
                console.log('update')
            }
        }

        //测试
        let dep = new Dep();
        let watcher = new Watcher();

        dep.addSub(watcher);
        dep.notify();

    </script>
</body>
</html>